Page 171 - Industrial Ventilation Design Guidebook

4.3 HEAT AND MASS TRANSFER I 3 3

The last term is best understood bv noting that

and then using the first part of Eq. (4.269).
Using Eq. (4.265) and c — C A + C B , the following connections result:

According to Eqs. (4,269) and (4.270),

Because p A — M Ac A, p B — M B c B ,and p — Me, whereM = (c A/c)M A + (c B/c)M B>

Substituting Eq. (4.271) in Eq. (4.268c) gives

For diffusion flow, p A(v Ax - v x), Fick's model (Eq. (4.241)) gives

Using important connections,

To shorten the notations, the following definition is used:

Using this, the mass flow density is represented as

and correspondingly for directions y and z. Substituting Eq. (4.276) into Eq.
(4.260) and keeping D AB constant gives

If the mixture density p = p A + p B is held constant, Eq. (4.264) gives